wip-new-core: Fix embedding for the JSON formatter output

features/docs/formatters/json_formatter.feature

@@ -263,7 +263,7 @@ Feature: JSON output formatter
       ]
       """
 
-  @wip-new-core
+  @spawn 
   Scenario: embedding screenshot
     When I run `cucumber -b --format json features/embed.feature`
     Then it should pass with JSON:

lib/cucumber/reports/legacy_formatter.rb

@@ -64,7 +64,6 @@ def initialize(runtime, formatters)
       extend Forwardable
 
       def_delegators :formatter,
-        :embed,
         :ask,
         :puts
 
@@ -85,6 +84,10 @@ def after_test_case(test_case, result)
         printer.after_test_case(test_case, result)
       end
 
+      def embed(src, mime_type, label)
+        printer.embed(src, mime_type, label)
+      end
+
       def done
         printer.after
       end
@@ -153,6 +156,10 @@ def after
           self
         end
 
+        def embed(src, mime_type, label)
+          @child.embed(src, mime_type, label)
+        end
+
         private
 
         def timer
@@ -181,6 +188,13 @@ def method_missing(name, node, step_result, *args)
         end
       end
 
+      Embedding = Struct.new(:src, :mime_type, :label) do
+
+        def send_to_formatter(formatter)
+          formatter.embed(src, mime_type, label)
+        end
+      end
+
       FeaturePrinter = Struct.new(:formatter, :runtime, :node) do
         include Debug
 
@@ -189,6 +203,7 @@ def before
           Legacy::Ast::Comments.new(node.comments).accept(formatter)
           Legacy::Ast::Tags.new(node.tags).accept(formatter)
           formatter.feature_name node.keyword, indented(node.name) # TODO: change the core's new AST to return name and description separately instead of this lumped-together field
+          @delayed_embeddings = []
           self
         end
 
@@ -209,6 +224,7 @@ def after_test_step(test_step, result)
         def after_test_case(*args)
           if current_test_step_source.step_result.nil?
             print_step_container
+            @delayed_embeddings = []
           end
           @child.after_test_case
           @previous_test_case_background = @current_test_case_background
@@ -256,6 +272,10 @@ def after
           self
         end
 
+        def embed(src, mime_type, label)
+          @delayed_embeddings << Embedding.new(src, mime_type, label)
+        end
+
         private
 
         def print_step_container
@@ -292,6 +312,14 @@ def print_step
           return unless current_test_step_source.step_result
           print_step_container
           @child.step(current_test_step_source.step, current_test_step_source.step_result)
+          print_embeddings
+        end
+
+        def print_embeddings
+          @delayed_embeddings.each do |embedding|
+            embedding.send_to_formatter(formatter)
+          end
+          @delayed_embeddings = []
         end
 
         def set_child_calling_before(child)